First Clinical Evaluation of Optical Fiber Sensor for Real-Time In-Vivo Dosimetry (RTIVD) During Seed Implantation for Prostate Low Dose Rate Brachytherapy

This research demonstrates a technique to add real-time in-vivo dosimetry (RTIVD) of actual point dose measurements at various positions of the prostate. A treatment plan was implemented, where Iodine-125 brachytherapy seeds, with an average activity of 0.410 mCi, were implanted into the prostate gland under trans-rectal ultrasound (TRUS) guidance. Images of implanted seeds were obtained using the VariSeed planning system following implantation of the seeds. Two complete brachytherapy clinical treatment plans were used to validate the RTIVD system. In this study we use an optical fibre sensor, incorporating radiation sensitive scintillation material, terbium doped gadolinium oxysulphide (Gd2O2S:Tb). This scintillation material is embedded in a 700μm diameter cavity within a 1mm plastic optical fibre, which is then secured within a brachytherapy needle. We use the high spatial resolution dosimeter to measure dose around the Iodine 125 sources and compare against the VariSeed planning system. The optical fibre dosimeters are designed for real-time in-vivo monitoring of the radiation dose during the implant procedure. It has been demonstrated that the in-vivo dosimetry system shows the potential to be a solution for providing radiation oncologists real-time information of the radiation dose to the target area (PTV) alongside the organs at risk (OARs).